reserve G for Go-board,
  i,j,k,m,n for Nat;

theorem Th11:
  for D being non empty set for f being non empty FinSequence of D
  for g being non trivial FinSequence of D st g/.len g = f/.1 holds f^'g is
  circular
proof
  let D be non empty set;
  let f be non empty FinSequence of D, g be non trivial FinSequence of D;
  assume g/.len g = f/.1;
  hence (f^'g)/.1 = g/.len g by FINSEQ_6:155
    .= (f^'g)/.len(f^'g) by FINSEQ_6:156;
end;
